In general, the preparation of foods such as pizza or salad requires convenient access by the preparer to ingredients or condiments such as dairy products, vegetables, meats and dough, etc., which are normally preserved in a state of "freshness" by refrigeration. Typically, quantities of different ingredients or condiments such as cheeses, peppers, mushrooms, sausage are kept in spearate trays for use by the food preparer for assembly into the finished foodstuff. The preparer works at a "make up" table where the separate ingredients are combined into the finished food product.
Problems occur in maintaining sufficient quantities of the ingredients conveniently available in a refrigerated state in a kitchen to preserve their freshness. Typically, ambient kitchen temperature is about 80.degree.-85.degree. F.; perishable foodstuffs must be maintained at about 40.degree. F. Thus, ice has been used to surround condiment or ingredient trays; and trays have been surrounded at their bottom and sides by circulating refrigerated air. These methods of maintaining the refrigerated temperature of foodstuff trays have not proven satisfactory, however, because the refrigeration generally reaches only the bottom and sides of the tray, and the top of the tray is exposed to ambient room heat. The temperature gradient through the volume or mass of the condiments in the tray is non-uniform. For example, icing may occur at the sides and bottom, and the top or center may be warm. Spoilage may occur. Storage of ingredients in an enclosed refrigerator is frequently inconvenient in a volume kitchen.
Dairy products are particularly prone to spoilage if not maintained at a refrigerated temperature below about 40.degree. to 45.degree. F. Above this temperature bacteria will grow. The problem of spoilage is not only a health concern but is also a matter of economic consequence in restaurant operations. For example, cheese is frequently the most expensive ingredient of a pizza; for this reason spoilage and waste of a voluable dairy product should be avoided.
In addition, many local health codes regulating the operation of food establishments require that the temperature of food ingredients be maintained at approximately 40.degree. F. so that bacteria growth, and the consequent risk of food poisoning is reduced.